This invention relates generally to the removal of sediment material from a body of water and, more particularly, to a method and apparatus for determining the depth of sediment material having a minimum desirable consistency or strength acceptable for removal from under a body of water via a dredging operation.
Various types of dredging equipment designed to remove sediment material from the bottom of a body of water are well known in the art. Such known dredging apparatus are usually designed to remove sediment from the floor of a body of water by excavating material at a particular predetermined depth below the surface of the water through the use of one or more excavating wheel assemblies. One such dredging apparatus is disclosed in U.S. Pat. No. 5,960,570.
The depth and consistency or strength of sediment material underneath a body of water are typically irregular and inconsistent as the floor surface of a particular body of water varies continually. Also, the consistency or strength of the sediment material to be removed normally varies as a function of depth below the surface of the floor, the upper portion or upper level of the sediment material at the floor surface having a very fine consistency or low strength. Given the costs associated with excavating, lifting and transporting removed material, it is desirable to remove sediment material having a higher consistency or strength, that is, material with higher silt or sediment content and lower water content. Therefore, material having a minimum consistency desirable for removal typically does not exist at the floor surface, but instead, such material typically exists at some depth below the floor surface of the body of water and that acceptable depth level usually varies throughout the terrain of the floor.
It is therefore desirable to accurately determine the depth of sediment material having a minimum desirable consistency throughout the floor surface of a body of water in order to adjust and control the depth of sediment removal during a dredging operation.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of this invention, an apparatus adapted for determining the depth of sediment material under a body of water having a minimum desirable consistency for a dredging operation is disclosed. The apparatus includes an arm assembly having opposed end portions, one end portion of the arm assembly being pivotally attached to a substantially horizontal member, a plate member associated with the opposite end portion of the arm assembly, the plate member having a predetermined cross-sectional area for encountering a resistance force from the sediment material located under the body of water when the plate member is moved thereacross, the resistance force from the sediment material causing the arm assembly to pivotally rotate relative to the substantially horizontal member, force means adapted to exert a biasing force on the arm assembly which acts against the resistance force of the sediment material, and the arm assembly achieving an equilibrium position when the biasing force equals the resistance force of the sediment material, the equilibrium position of the arm assembly determining the depth of the sediment material having a minimum desirable consistency for a dredging operation.
In another aspect of this invention, a method for determining the depth of sediment material having a minimum desirable consistency under a body of water wherein a dredging apparatus is used to remove the sediment material from under the body of water, the dredging apparatus having a frame structure and a dredging wheel mechanism associated therewith. The method includes the following steps of providing an arm assembly having opposed end portions, providing a substantially horizontal member for attaching to the dredging apparatus, pivotally mounting the arm assembly to the substantially horizontal member, providing a plate member associated with the opposite end portion of the arm assembly, the plate member having a predetermined cross-sectional area for encountering a resistance force from the sediment material when the plate member is moved thereacross, the resistance force from the sediment material causing the arm member to pivotally rotate relative to the substantially horizontal member, moving the arm assembly across the sediment material located under the body of water, applying a force on the arm assembly opposing the resistance force exerted on the plate member by the sediment material, the arm assembly achieving an equilibrium position when the opposing force equals the resistance force of the sediment material, the equilibrium position determining the depth of the sediment material having a minimum desirable consistency for a dredging operation, sensing the angular position of the arm assembly relative to a predetermined referenced orientation when the arm assembly is in its equilibrium position, and determining the depth of the equilibrium position of the arm assembly with respect to the frame structure of the dredging apparatus based upon the sensed angular position of the arm assembly at its equilibrium position.